2,2-Dimethoxy-2-phenylacetophenone: photochemistry and free radical photofragmentation

Abstract

Radical reactions induced by photocleavage of the photocuring agent 2,2-dimethoxy-2-phenylacetophenone in oxygen-free solutions are investigated by product Analysis, CIDNP, and by optical and ESR spectroscopy. It is shown that the photochemistry of the title compound is strongly influenced by both thermal and photochemical fragmentations of the α,α-dimethoxybenzyl radical. A resulting light intensity dependence of product distributions and spectra has caused previous misinterpretations of reaction mechanisms, reaction kinetics, and spectral assignments. Detailed mechanisms, optical spectra, and kinetic data on self-terminations, thermal fragmentations, and additions to acrylonitrile of dimethoxybenzyl, benzoyl, and related radicals are reported.